1. Field of the Invention
The present invention relates to photolithographic techniques in semiconductor processing, and, more particularly, to the deposition of deep submicron metallization within high aspect ratio semiconductor structures.
2. Description of the Related Art
In the construction of integrated circuit devices, one or more metallic layers, such as aluminum, copper or titanium, are deposited and subsequently patterned to provide ohmic or Schottky contacts and electrical connections between various circuit elements. Conventionally, photoresist is spun over the metallic layer and then exposed to a light pattern and developed. The normally aluminum metallic layer is then selectively plasma-etched with chlorine-containing gases through the openings in the resist layer. The remaining photoresist is then removed, leaving the final metal pattern.
Antireflective coatings (ARC's) have been applied over reflective surfaces such as aluminum, copper or titanium to improve resist patterning control by reducing interference effects and diffuse scattering, particularly if the illumination source used is monochromatic. Such effects have become less and less tolerable, however, as linewidth and pitch have been reduced in newer integrated circuit designs of greater density.
One approach to reduce the reflected light has been to use metal or refractory materials as antireflective films on aluminum. The titanium nitride films currently used for metal layer antireflective coatings and via etch stop functions, however, are not compatible with deep layer ultraviolet photoresists. As integrated circuit design geometries shrink, deep level ultraviolet photolithography has been used to deposit metals in trenches, contacts and/or via structures. The use of silicon oxynitride as an antireflective coating has been proposed by Gocho et al. in "Chemical Vapor Deposition of Anti-Reflective Layer Film for Excimer Laser Lithography," Japanese Journal of Applied Physics, Vol. 33, Part 1, No. 1B, pp. 489-494 (January 1994). However, no reference was made to the use of silicon oxynitride films for multi-layer interconnect structures now being used in high density integrated circuit manufacturing.
In order to manufacture multi-layer interconnect structures, embedded or burried trenches, vias and/or contacts have been created to achieve electrical contact between layers of metal interconnect. In order to employ such structures within the multiplicity of layers deposited to form an integrated circuit, it is necessary to accurately control and stop certain photolithographic steps from penetrating beyond the precise layers being connected to each other. Etch stopping agents are commonly used to prevent such effects. The prior art, however, does not address the use of silicon oxynitride as an etch stop in the formation of such structures.
Further, Sturtevant et al. in "Substrate Contamination Effects in the Processing of Chemically Amplified DUV Photoresists," SPIE, Vol. 2197, pp. 770-780, and Usijima et al. in "Effects of Substrate Treatment in Positive Chemically-Amplified Resist," SPIE, Vol. 2438, pp. 529-539, address the use of oxidizing plasmas to treat metallic surfaces. However, neither of these references specifically address the use of oxidizing plasmas to treat silicon oxynitride surfaces. One approach to the use of oxidizing plasmas to treat silicon oxynitride surfaces is disclosed in co-pending application Ser. No. 08/857,055, entitled "Process For Forming Bottom Anti-Reflection Coating For Semiconductor Fabrication Photolithography Which Inhibits Photoresist Footing," filed on May 15, 1997, and commonly owned by the assignee of the present application, the contents of which are hereby incorporated herein by reference.
What is lacking in the art is the use of silicon oxynitride films both as antireflective coatings and etch stops within deep submicron metallization structures in semiconductor integrated circuits. Such structures are commonly patterned using photoresists having deep ultraviolet wavelengths, which are prone to be reflected by metallic surfaces and which must be properly controlled in the creation of interconnect vias and contacts.